Manufacturing of hard masks for patterning magnetic media

ABSTRACT

Embodiments of the present invention relate to systems and methods for designing and manufacturing hard masks used in the creation of patterned magnetic media and, more particularly, patterned magnetic recording media used in hard disk drives (e.g., bit patterned media (BPM)). In some embodiments, the hard mask incorporates at least one layer of Ta (tantalum) and at least one layer of C (carbon) and is used during ion implantation of a pattern onto magnetic media. The hard mask can be fabricated with a high aspect ratio to achieve small feature sizes while maintaining its effectiveness as a mask, is robust enough to withstand the ion implantation process, and can be removed after the ion implantation process with minimal damage to the magnetic media.

TECHNICAL FIELD

This invention relates to the field of disk drives and morespecifically, to hard masks for patterning magnetic recording media fordisk drives.

BACKGROUND

When manufacturing of patterned magnetic recording media (e.g., bitpatterned media (BPM) or discrete track media (DTM)), an ionimplantation process may be utilized to transfer the pattern of apatterned resist layer to a magnetic layer of the magnetic recordingmedia. Usually, during such implantation process, a hard mask isdisposed over the magnetic layer to allow ion penetration at certainareas of the media's magnetic layer (also known as ion implantedregions) while preventing ion penetration at others (also known asnon-ion implanted regions). Those areas of the exposed to the ions areknown to exhibit suppressed or substantially reduced magnetic moment incomparison to those areas protected from ions penetration; thisdifference in magnetic moment result in the pattern magnetic layer.

Typically, for a hard mask to be effective during ion implantation, itmust be: (1) capable of stopping the ions from reaching the magneticlayer of the media (which is usually dictated by material composition,density, and mask thickness); (2) extendible to high density or smallfeature sizes for patterned magnetic recording media (e.g., for BPM,which require a high aspect ratio mask to maintain a thick mask forprotection); (3) robust enough to withstand the etching effects of theion implantation process such that the hard mask is not substantiallyremoved or altered during the ion implantation process; and (4)removable such that after the ion implantation process it can easilyremoved without damaging the magnetic layer in the process.

Unfortunately, no single conventional masking configuration meets all ofthese requirements. For instance, when patterning a magnetic layer usingion implantation with nano-imprint lithography (NIL), the resistmaterial used easily etches away during ion implantation, therebyresulting in less sharp transitions in the magnetic layer between areasof the magnetic layer exposed to ions (i.e., ion implanted regions) andareas not exposed to ions (i.e., non-implanted regions). In anotherexample, when a single metal hard mask comprising Ta is used inconjunction with ion implantation, the aspect ratio is usually notextendible to small features, due to the patterned resist thicknessdecreasing as feature size decreases while the relative etch rates ofthe resist and Ta are constant. Furthermore, for single metal hard masksthat comprise Ta usually can not be removed from the magnetic mediawithout damaging the underlying magnetic layer (the fluorine-based dryetch chemistries required for removal damage the magnetic layer).

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and notlimitation, in the figures of the accompanying drawings in which:

FIG. 1 illustrates a flowchart of a method for manufacturing a magneticrecording medium in accordance with one embodiment of the presentinvention;

FIGS. 2-8 illustrate a cross-sectional view of a magnetic recordingmedium being manufactured in accordance with an embodiment of thepresent invention;

FIG. 9 illustrates a flowchart of a method for manufacturing a magneticrecording medium in accordance with an embodiment of the presentinvention;

FIGS. 10-18 illustrate a cross-sectional view of a magnetic recordingmedium being manufactured in accordance with an embodiment of thepresent invention;

FIGS. 19 and 20 provide electron microscope images of magnetic recordingmedia manufactured in accordance with an embodiment of the presentinvention; and

FIG. 21 illustrates a disk drive including a patterned magneticrecording disk fabricated in accordance with one embodiment of thepresent invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth,such as examples of specific layer compositions and properties, toprovide a thorough understanding of various embodiment of the presentinvention. It will be apparent however, to one skilled in the art thatthese specific details need not be employed to practice variousembodiments of the present invention. In other instances, well knowncomponents or methods have not been described in detail to avoidunnecessarily obscuring various embodiments of the present invention.

The terms “over,” “under,” “between,” and “on” as used herein refer to arelative position of one media layer with respect to other layers. Assuch, for example, one layer disposed over or under another layer may bedirectly in contact with the other layer or may have one or moreintervening layers. Moreover, one layer disposed between two layers maybe directly in contact with the two layers or may have one or moreintervening layers. In contrast, a first layer “on” a second layer is incontact with that second layer. Additionally, the relative position ofone layer with respect to other layers is provided assuming operationsare performed relative to a substrate without consideration of theabsolute orientation of the substrate.

Embodiments of the present invention relate to systems and methods fordesigning and manufacturing hard masks used in the creation of patternedmagnetic media and, more particularly, patterned magnetic recordingmedia used in hard disk drives (e.g., bit patterned media (BPM)). Insome embodiments, the hard mask incorporates at least one layer of Ta(tantalum) and at least one layer of C (carbon) and is used during ionimplantation of a pattern onto magnetic media. Some such Ta/C hard masksare capable of: (1) stopping the ions from reaching the magnetic layerof the magnetic media; (2) being fabricated with high aspect ratio toachieve high density or small feature sizes for patterned magneticrecording media (e.g., for BPM) while maintaining mask effectiveness;(3) withstanding the etching effects of the ion implantation processsuch that the hard mask is not substantially removed or altered duringthe ion implantation process; and (4) being removed after the ionimplantation without damaging the magnetic layer in the process.

FIG. 1 illustrates a flowchart 100 of an example method for creatingmagnetic recording media, in accordance with one embodiment, using asingle tantalum layer and single carbon layer mask (i.e., single Ta/Chard mask). The illustrated method begins at operation 101 with thedeposition of a carbon (C) layer over a magnetic recording layer of amagnetic recording medium. The magnetic recording layer may be over asoft magnetic underlayer (SUL), a non-magnetic interlayer between themagnetic recording layer and SUL, and a bottom substrate. The carbonlayer may be deposited using chemical vapor deposition (CVD) andrelatively thick (e.g., ˜40 nm) in comparison to other layers of themagnetic recording medium. Next, at operation 104, a layer of tantalum(Ta) is deposited over the carbon layer. The tantalum layer may berelatively thin in comparison to the carbon layer and deposited using asputtering methodology. Tantalum, compared to other materials, exhibitsgood etch resistance to ion implantation processes. For example, undertypical implantation conditions, 1 nm of Ta is removed while at the sameimplant conditions, 30 nm of photoresist would have been etched away.

Following tantalum deposition, a photoresist layer is deposited andpatterned using lithographic techniques at operations 107 and 110respectively. The lithography technique utilized may be nano-imprintlithography (NIL). In some embodiments, the tantalum layer issufficiently thin enough to allow thin photoresist layers to betransferred into the tantalum layer without completely etching away theresist, while being sufficiently thick enough to protect the thickcarbon layer underneath (i.e., thick enough to be effective as aprotective mask for the carbon layer). For example, the tantalum layermay have a thickness between 1 nm and 2 nm. By being able to use thinpatterned resist layers, pattern feature sizes can be correspondinglyreduced (e.g., <25 nm for BPM), which allows for higher areal density,among other things. The thick carbon layer underlying the relatively thetantalum layer is thick enough to provide good mask protection duringthe ion implantation process.

FIGS. 2 and 3 depict an example magnetic recording medium subsequent tooperations 101-110. FIG. 2 illustrates a cross-sectional depiction ofmagnetic recording medium 200 comprising a substrate layer 213, amagnetic recording layer 210, a (thick) carbon layer 207, a (thin)tantalum layer 204, and a photoresist layer 201. FIG. 3 depicts the samemagnetic recording medium 200 after photoresist layer 201 has beenpatterned into photoresist patterned layer 216. It should be noted thatat the bottom 220 of the each feature of photoresist patterned layer216, there remains a thin layer of photoresist layer. In someembodiments, this thin layer of photoresist is removed when thephotoresist patterned layer is transferred to the underlying tantalumlayer.

Continuing with the method of FIG. 1, at operation 113, the resultingphotoresist patterned layer is transferred to the tantalum layer suchthat the two layers share the same pattern. This results in a tantalumpatterned layer that functions as a tantalum mask. The transfer may beperformed, for example, by way of a plasma dry etching usingfluorine-based gas chemistries, such as CF₄, which can etch through athin photoresist layer (e.g., at 220) and etch the tantalum layer.

FIG. 4 illustrates magnetic recording medium 200 once photoresistpatterned layer 216 has been transferred to tantalum layer 204,resulting in photoresist patterned layer 219 and tantalum patternedlayer 224. As depicted, the thin layer of photoresist depicted in FIG. 3(at 220) is now removed in photoresist patterned layer 219 (see, 221) byway of the dry etch process used to transfer photoresist patterned layer216 to tantalum layer 204.

Continuing with the method of FIG. 1, at operation 116, the tantalumpatterned layer is transferred to the carbon layer, thereby resulting ina carbon patterned layer that functions as a carbon mask. For example,the transfer may be performed by way of a plasma dry etching usingoxygen-base chemistries, such as Ar—O₂ plasma, which do not etch thetantalum pattern layer. The carbon layer may be etched such that aresidual layer of carbon is left at the bottom of each carbon etchfeature; this residual carbon layer is later used to protect themagnetic recording layer when the tantalum patterned layer is laterremoved (after the ion implantation process). As a result of the thintantalum mask, a high aspect ratio is maintained in the carbon patternedlayer. FIG. 5 depicts magnetic recording medium 200 after tantalumpatterned layer 224 is transferred to carbon layer 207, resulting incarbon patterned layer 227.

Optionally, the photoresist patterned layer is removed at operation 119.However, in some embodiments, the etch process used to transfer thetantalum patterned layer to the carbon layer causes most if not all thephotoresist patterned layer to be removed. In such embodiments, ifportions of the photoresist patterned layer remain after the transfer ofthe tantalum patterned layer to the carbon layer, those portions wouldbe removed by etch processes subsequent to the implantation process.

Subsequent to operation 116, the ion implantation process is performed(at operation 122) to pattern the magnetic recording layer. FIG. 6depicts the ion implantation process 230 being performed on magneticrecording medium 200 after photoresist patterned layer 219 has beenremoved.

After the implantation process, tantalum (patterned) layer mask 224 andthe carbon (patterned) layer mask 227 are removed, as depicted in FIGS.7 and 8 respectively. Removal may be facilitated using dry etch. Forexample, the tantalum layer may be removed using fluorine-based gaschemistries (e.g., CF₄) and the carbon layer may be removed usinghydrogen-based chemistries (e.g., Ar—H₂ or H₂ plasma). Because amagnetic recording layer can be easily damaged by the CF₄ plasma and theetch rate of tantalum using CF₄ is higher than the etch rate of carbon,a residual layer of carbon (240) may be left remaining in carbon etchfeatures so that the tantalum layer mask layer can be removed using CF₄before the CF₄ completely etches away the residual carbon layer.

As depicted in FIG. 8, once the tantalum layer has been removed, thesole remaining carbon (patterned) layer mask 227 may be removed by dryetching (e.g., Ar—H2 or H2 plasma) with minimal damage to the magneticrecording layer 210.

FIG. 9 illustrates a flowchart 900 of an example method for creatingmagnetic recording media, in accordance with an embodiment, using a hardmask comprising more than one layer of tantalum and more than one layerof carbon (e.g., a dual Ta/C hard mask). The method begins at operation901 with the deposition of a first carbon (C) layer over a magneticrecording layer of a magnetic recording medium. The first carbon layerwill be relatively thin (e.g., ˜2 nm) in comparison to other layers ofthe magnetic recording medium. This is followed by the deposition of afirst tantalum (Ta) layer over the carbon layer at operation 904. Thefirst tantalum layer will also be relatively thin (e.g., ˜1 nm) incomparison to other layers of the magnetic recording medium. Asdescribed later below, in some embodiments, the first carbon layer andfirst tantalum layer can be useful in the removal of the hard masklayers from the magnetic recording layer after the ion implantationprocess. Subsequently, operations 907-928 of FIG. 9 mirror operations101-122 of FIG. 1.

At operation 907, a second carbon (C) layer is deposited over the firstcarbon layer. The second carbon layer may be deposited using chemicalvapor deposition (CVD) and relatively thick (e.g., ˜40 nm) in comparisonto other layers of the magnetic recording medium. At operation 910, asecond tantalum (Ta) layer is deposited over the second carbon layer.Then, at operation 913 a photoresist layer is deposited over the secondtantalum layer. At operation 916 the photoresist layer is patternedusing a lithographic technique, such as nano-imprint lithography (NIL),thereby resulting in a photoresist patterned layer.

FIG. 10 illustrates the results of operations 901-913 in an examplemagnetic recording medium 300. Medium 300 comprises a substrate layer319, a magnetic recording layer 316, a (thin) first carbon layer 313, a(thin) first tantalum layer 310, a (thick) second carbon layer 307, a(thin) second tantalum layer 304, and a photoresist layer 301. FIG. 11illustrates the result of operation 916, where photoresist layer 301 ispatterned into photoresist patterned layer 322. It should be noted thatat the bottom 320 of the each feature of photoresist patterned layer322, there remains a thin layer of photoresist layer. In someembodiments, this thin layer of photoresist is removed when thephotoresist patterned layer is transferred to the underlying tantalumlayer.

Continuing with FIG. 9, at operation 919, the resulting photoresistpatterned layer is transferred to the second tantalum layer such thatthe two layers share the same pattern. This results in a tantalumpatterned layer that functions as a tantalum mask. The transfer may beperformed, for example, by way of a plasma dry etching usingfluorine-based gas chemistries, such as CF₄, which can etch through athin photoresist layer (e.g., at 320) and etch the second tantalumlayer.

FIG. 12 illustrates magnetic recording medium 300 once photoresistpatterned layer 322 has been transferred to second tantalum layer 304,resulting in photoresist patterned layer 325 and tantalum patternedlayer 328. As shown, the thin layer of photoresist depicted in FIG. 11(at 320) is now removed in photoresist patterned layer 325 (see, 321) byway of the dry etch process used to the transfer photoresist patternedlayer 322 to tantalum layer 304.

Moving on to operation 922 of FIG. 9, the tantalum patterned layer istransferred to the second carbon layer, thereby resulting in a carbonpatterned layer that functions as a carbon mask. For example, thetransfer may be performed by way of a plasma dry etching usingoxygen-base chemistries, such as Ar—O₂ plasma, which do not etch thetantalum patterned layer. The carbon layer may be etched such that aresidual layer of carbon is left at the bottom of each carbon etchfeature. Unlike the method of FIG. 1, this residual carbon layer is nolonger needed to protects the magnetic recording layer during hard masklayer removal (after the ion implantation process) but, rather, thefirst tantalum layer during removal of the second carbon layer. FIG. 13depicts magnetic recording medium 300 after tantalum patterned layer 328is transferred to second carbon layer 307, resulting in carbon patternedlayer 331.

Once the photoresist patterned layer is removed at operation 925, theion implantation process is performed (at operation 928) to pattern themagnetic recording layer. FIG. 14 depicts magnetic recording medium 300the ion implantation process 334 being performed on magnetic recordingmedium 300 after photoresist patterned layer 325 has been removed.

After the implantation process, tantalum (patterned) layer mask 328 andthe carbon (patterned) layer mask 331 are removed, as depicted in FIGS.15 and 16 respectively. As before, removal of tantalum patterned layer328 and carbon patterned layer 331 can be facilitated using dry etch.For example, the tantalum patterned layer may be removed usingfluorine-based gas chemistries (e.g., CF₄) and the carbon patternedlayer may be removed using hydrogen-based chemistries (e.g., Ar—H₂ or H₂plasma). First tantalum layer 310 at the bottom of the etched featuresof tantalum patterned layer 328 and carbon patterned layer 331 is notexposed during the removal of either the tantalum patterned layerbecause of the residual carbon layer left after the tantalum patternedlayer is transferred to the second carbon layer (i.e., after operation922); the residual carbon layer functions as an etch stop during theetch processes that removes tantalum patterned layer 328. Then, whencarbon patterned layer 331 is removed, first tantalum layer 310 functionas an etch stop to prevent the etch process that removes carbonpatterned layer 331 from damaging the magnetic recording layer.

Once the thin tantalum mask (i.e., tantalum patterned layer 328) and thethick carbon mask (i.e., carbon patterned layer 331) have been removed,the first thin tantalum layer (i.e., first tantalum layer 310) and firstthin carbon layer (i.e., first carbon layer 313), can be etched awayusing, for example, a dry etch process (e.g., CF₄ and Ar—H₂ plasma,respectively). FIGS. 17 and 18 respectively depict magnetic recordingmedium 300 after first tantalum layer 310 is removed and first carbonlayer 313 is removed.

Because of the uniform thickness of the first tantalum layer and thefirst carbon layer, the dry etch process can remove the tantalum layerand carbon layer uniformly without any area of the magnetic recordinglayer being overly exposed to the etch chemistries used for removal(e.g., CF₄ and Ar—H₂ plasma). The use of the first tantalum layer andthe first carbon layer in conjunction with the second tantalum layer andthe second carbon layer helps avoid situations where exposure of themagnetic recording layer to etch chemistries used during removal of thecarbon (patterned) layer mask (e.g., Ar—H₂ or H₂ plasma) are greater inthe etched carbon features (where the residual carbon is much thinner)than the non-etched areas (where the carbon mask is thicker).

In some embodiments, a dual Ta/C hard mask allows for a reduction infeature size from resist mask to Ta/C mask. For example, a 30 nm widefeature in a photoresist mask can be reduced to a 13 nm wide feature ina dual Ta/C mask, thereby alleviating difficulty in fabricating smallfeatures. In other embodiments, a dual Ta/C hard mask is extendible tohigh density or small features, whereby the dual Ta/C hard mask allowsfor a thick hard mask to stop ions while maintaining small featuredimensions (i.e., high aspect ratio). This is achieved because the firsttantalum layer masks the first carbon layer and the first tantalum layeris not etched while the second carbon layer is etched. This in contrastto other approaches, where the hard mask thickness will have to bereduced as features get smaller; these thinner hard masks will not beeffective at stopping ions. In further embodiments, a dual Ta/C hardmask exhibits high aspect ratio features with steep side-wall angle,which help to produce sharp transition between implanted andnon-implanted region of magnetic layers.

FIG. 19 provides scanning electron microscope (SEM) images of linesetched into a single Ta/C hard mask on a magnetic recording medium tocreate a discrete track medium (DTM) (perspective view 355,cross-sectional view 357). The groove depth is ˜44 nm and the groovewidth is ˜21 nm. In comparison, the original groove width in patternedphotoresist used to create the single Ta/C hard mask was ˜30 nm. Thephotoresist is not shown because it was etched away during the etchprocess that removed the carbon layer.

FIG. 20 provides a transmission electron microscope (TEM) image ofgrooves (360) etched into a single Ta/C hard mask on a magneticrecording medium to create a discrete track medium (DTM). The groovedepth is ˜44 nm and the groove width is ˜21 nm. In contrast, theoriginal groove width of the patterned photoresist used to create thesingle Ta/C hard mask was ˜30 nm. There is no photoresist remainingbecause it was etched away during the etch process that removed thecarbon layer. The sidewall angle is steeper in the etched Ta/C featuresthan in original patterned resist features.

FIG. 21 illustrates a disk drive 400 having disk 401. Disk drive 400 mayinclude one or more disks 400 to store data. Disk 401 resides on aspindle assembly 460 that is mounted to drive housing 480. Data may bestored along tracks in the magnetic recording layer of disk 401 whichare patterned using methods similar or identical to those discussedherein. For example, disk 401 may be a bit patterned medium (BPM). Thereading and writing of data is accomplished with head 450 that has bothread and write elements. The write element is used to alter theproperties of the perpendicular magnetic recording layer of disk 401. Inone embodiment, head 450 may have magneto-resistive (MR), or giantmagneto-resistive (GMR) elements. In an alternative embodiment, head 450may be another type of head, for example, an inductive read/write heador a Hall effect head. A spindle motor (not shown) rotates spindleassembly 460 and, thereby, disk 401 to position head 450 at a particularlocation along a desired disk track. The position of head 450 relativeto disk 401 may be controlled by position control circuitry 470.

In the foregoing specification, embodiments of the invention have beendescribed with reference to specific exemplary features thereof. Itwill, however, be evident that various modifications and changes may bemade thereto without departing from the broader spirit and scope of theinvention as set forth in the appended claims. The specification andfigures are, accordingly, to be regarded in an illustrative rather thana restrictive sense.

What is claimed is:
 1. A method for manufacturing a magnetic recordingmedium, the method comprising: depositing a first carbon (C) layer overa magnetic layer of the magnetic recording medium; depositing a firsttantalum (Ta) layer over the first carbon layer; depositing a secondcarbon (C) layer over the first tantalum layer; depositing a secondtantalum (Ta) layer over the second carbon layer; depositing aphotoresist layer over the second tantalum layer; patterning thephotoresist layer to form a photoresist patterned layer; transferringthe photoresist patterned layer into the second tantalum layer to form atantalum patterned layer; transferring the tantalum patterned layer intothe second carbon layer to form a carbon patterned layer; and performingan implantation process.
 2. The method of claim 1, wherein the firstcarbon layer has a first thickness and the second carbon layer has asecond thickness that meets or exceeds the first thickness.
 3. Themethod of claim 1, wherein the first carbon layer has a thickness ofapproximately 2 nm.
 4. The method of claim 1, wherein the first tantalumlayer has a thickness of approximately 1 nm.
 5. The method of claim 1,wherein the second carbon layer is etched such that etched features ofthe second carbon patterned layer have residual carbon layer remaining.6. The method of claim 1, further comprising removing the secondtantalum layer and removing the second carbon layer.
 7. The method ofclaim 6, wherein removing the second tantalum layer comprises dryetching using a fluorine-based gas chemistry.
 8. The method of claim 6,wherein removing the second carbon layer comprises dry etching using anoxygen-based gas chemistry.
 9. The method of claim 1, further comprisingremoving the first tantalum layer and removing the first carbon layer.10. The method of claim 9, wherein removing the first tantalum layercomprises dry etching using a fluorine-based gas chemistry.
 11. Themethod of claim 9, wherein removing the first carbon layer comprises dryetching using a hydrogen-based gas chemistry.
 12. The method of claim 1,wherein transferring the tantalum patterned layer to the second carbonlayer comprises dry etching using an oxygen-based gas chemistry.
 13. Themethod of claim 1, wherein transferring the photoresist patterned layerto the second tantalum layer comprises dry etching using afluorine-based gas chemistry.
 14. The method of claim 1, wherein thesecond tantalum layer has a thickness sufficient to still cover thesecond carbon layer subsequent to the photoresist patterned layer beingetched into the second tantalum layer.
 15. The method of claim 1,wherein the second tantalum layer has a thickness sufficient to protectthe second carbon layer subsequent to the photoresist patterned layerbeing etched into the second tantalum layer.
 16. The method of claim 1,wherein the second tantalum layer has a thickness between approximately1 nm and 2 nm.